1. Field of the Invention
This invention relates to internal combustion engines and more particularly to an improved rotary valve for internal combustion engines having capacity for a high rate of air flow at all ranges of engine revolutions per minute (R.P.M.), as well as having provision for inclusion of the spark plug within the structure of the rotary valve, an aspiration assistance device, and an advance and retard mechanism.
2. Description of the Prior Art
Internal combustion engines require selective aspiration of the cylinders in order to function properly. During the intake and exhaust strokes of the cycle, aspiration is provided in order that a combustible gas be admitted into the cylinder and the combusted gas be exhausted from the cylinder, respectively. During the compression and power strokes of the cycle, aspiration is prevented in order that the combustible gas be compressed by the piston prior to ignition and expanded against the piston after ignition, respectively.
Conventionally, selective control over aspiration of internal combustion engine cylinders has been almost universally achieved by use of tappet valves. Tappet valves have been favored because of their ability to seal the combustion chamber with a minimum of wear while providing minimal exhaust and lubricant blow-by. Unfortunately, tappet valves require cam shafts, rocker arms, springs, and lifters in order to operate. This complex grouping of parts, all of which require lubrication, adds to the cost of the engine as well as to the chances for a malfunction. Further, a minimum of two tappet valves must be provided for each cylinder, one for the exhaust function and the other for the intake function. Because tappet valves operate by reciprocation, the impact on the valve seat during each cycle frequently results in noisy operation. Noisy operation can also result from the rocker arms and lifters not following properly. Additionally, tappet valves have a large head surface which is separated from the valve seat when aspiration is initiated. The head is oriented perpendicular to the valve seat opening and, consequently, is in the way of exhaust and intake gases, thereby causing gas flow impedance. Finally, tappet valves tend to get very hot during operation of an internal combustion engine because of their continuous presence within the combustion chamber. As a result, they can become red hot and serve as sites for preignition of the combustible gas.
The foregoing problems may be solved by utilizing rotary valves, instead of tappet valves. Because rotary valves rotate rather than reciprocate, operation is noiseless and vibration free. Further, there is no need for a cam shaft, rocker arms, springs, and lifters, thus eliminating their associated problems. Additionally, because there is no head structure on the rotary valve, the aperture for aspiration is clear of interfering objects that may impede gas flow. These benefits result in improved engine efficiency and power. Finally, because the rotary valve rotates rather than reciprocates, it has no portion which is at all times in communication with the combustion chamber. Consequently, no hot spots are present and the preignition problem associated with tappet valves is eliminated.
Rotary valves for internal combustion engines can broadly be classified as being either of a disk type or a drum type. An example of a disk type rotary valve is U.S. Pat. No. 2,648,318 to Bensinger which discloses a single rotating disk having apertures therein for selective control over aspiration of the cylinder. Other examples are U.S. Pat. No. 4,418,658 to DiRoss which discloses a disk type rotary valve for each of the aspiration functions, intake and exhaust, and U.S. Pat. No. 2,444,696 to De La Riestra et al which discloses a disk-like rotary valve having a dome structure.
A drum type rotary valve is generally cylindrically shaped, has apertures on its surface for selective alignment with chamber openings in the engine, and may be oriented either parallel or perpendicular in relation to the axis of the cylinder for the piston. Examples of drum type rotary valves oriented parallel with the cylinder are U.S. Pat. Nos. 1,282,60 to Lindstrom, 2,283,594 to Aspin and 3,130,953 to Carpenter. Examples of drum type rotary valves oriented perpendicular to the cylinder are U.S. Pat. Nos. 1,188,656 to Hoff, 1,692,396 to Tipton, 2,369,147 to Klas, and 2,975,774 to Coffey et al. Further, examples of dual drum type rotary valves which are oriented perpendicular to the cylinder, one being provided for each of the intake and exhaust aspiration functions, are U.S. Pat. Nos. 4,077,382 to Gentile, 4,473,041 to Lyons et al, and 4,545,337 to Lyons et al. A variation in rotary valve structural shape is disclosed in U.S. Pat. No. 2,787,988 to Genet, which teaches a rotary valve having a part spherically shaped portion mated to a cylindrically shaped portion.
U.S. Pat. No. 2,257,846 to Horstman discloses a rotary valve having fuel injectors for a diesel cycle internal combustion engine enclosed in the drum structure.
Widespread use of rotary valves has been hindered by sealing problems, especially as related to lubrication and frictional power loss. Examples of teachings which address this problem area are as follows. U.S. Pat. No. 1,751,986 to Flescher discloses an early solution for lubrication delivery problems by having a plurality of pockets with rollers received therein for oiling the rotary valve. U.S. Pat. No. 3,990,423 to Cross et al discloses lip seals on the rotary valve seat. A head having a separate sealed cap retained by a crossbar keeps the rotary valve on the lip seals during the compression stroke. Finally, U.S. Pat. No. 4,517,938 to Kruger discloses a rotary valve having drive bearings and drive bearing seals. As a result of improvements such as these, combined with the clear advantages of the rotary valve over the tappet valve, rotary valves can now offer superior performance in today's internal combustion engines.
There remains, however, a problem in the art to devise a single rotary valve for each cylinder of an internal combustion engine which provides the inherent operational advantages that tappet valve engine configurations allow, namely, positioning the spark plug at the axial centerline of the cylinder and aspirating the cylinder at the top end thereof. Further, there remains the need in the art to provide an aspiration assistance device for the rotary valve that provides increased aspiration efficiency, resulting in better performance of the engine.